Optimization of regional hazardous waste management systems: an improved formulation

The planning and design of regional hazardous waste management system (RHWMS) involves selection of treatment and disposal facilities, allocation of hazardous wastes and waste residues from generator to the treatment and disposal sites and selection of the transportation routes. An improved formulation based upon multi-objective integer programming approach is presented to arrive at the optimal configuration of RHWMS components. This formulation addresses important practical issues like unique characteristics of the hazardous wastes reflecting on waste-waste and waste-technology compatibility. A utility function approach is presented to integrate both cost and risk related objectives. An illustrative case example is presented to demonstrate the usefulness of the improved formulation as a tool which can be used by environmental planning agencies in regional planning for hazardous waste management. (C) 1999 .

Non-uniform field breakdown of SF6SF_6 insulation under combined DC and switching impulse voltages

A number of rod-plane gaps in $SF_6$ gas prestressed by DC voltages have been tested under positive switching impulse voltages and the effect of the composite stresses on the breakdown probability distribution have been investigated. Experiments were carried out using positive switching impulse voltages superimposed on positive and negative DC voltages at a constant gap separation of 25 mm over the pressure range of 0.1 to 0.5 MPa (absolute) with the degree of field nonuniformity being varied systematically using various rod diameters, i.e. a sharp point, 1.59 mm, 3 mm, 6 mm and 12 mm and a plane electrode 210 mm in diameter. The results clearly show that the DC pre-stressing of the nonuniform field gap considerably alters the breakdown probabilities as well as corona stabilization and breakdown voltages. The results are presented and discussed in the pape